Subsystems tests are functionally grouped and
mode oriented so that related functions can be chal-
lenged using the same setup, procedures, and stimuli.
Where practical, subsystems tests use tactical indi-
cators for measurement, leaving the requirement for
special hookups and test equipment to equipment-
A major combat ship contains most, or all, of the
Command and control subsystem
Gun/missile weapon subsystem
External communications subsystem
Equipment testing is defined as testing that is
generally directed toward power levels, frequencies,
servos, special features, and output functions. The
PMS may require special external stimulating equip-
ment and special- or general-purpose test equipment
for testing measurements.
The objective of fault isolation is the systematic
application of fault-isolation tools needed to isolate
the exact unit or fictional interface responsible for a
fault or degraded operation during testing or tactical
operation. To diagnose and effect timely repair of
faults within a fire-control system, you must fully
understand fault-isolation concepts, the fault-isolation
tools available to you, and the capabilities and limita-
tions of those tools when applied to system fault iso-
3. It conveys the maximum intelligence regard-
ing the source of the fault.
Although the primary entry into fault isolation is
from test-detected faults, improper operating condi-
tions can be observed during tactical operations,
including operator awareness, data extraction and re-
duction, and on-line monitoring.
Fault isolation leads to corrective maintenance.
After a fault has been isolated to a specific unit or
interface, corrective action in the form of repair, re-
placement, and/or alignment must be taken. The
corrective maintenance performed may or may not be
required to return the system to an operable condition.
There may have been more than one fault contributing
to the out-of-tolerance condition that initiated the
fault-isolation process. The possibility of faulty re-
placement parts and incorrect adjustment or alignment
exists. Instead of solving the problem, corrective
maintenance may have added to it. Therefore, it is
mandatory that each corrective action be followed by
Normally, verification is accomplished by re-
creating the test environment and rechallenging the
function. Where alignments are concerned, the inter-
dependent effect upon other elements of the combat
systems must be considered in the verification pro-
During testing or operational use of a weapons
system, faults can occur in the interface between sub-
systems, in the interface between equipments of a
subsystem, or in the equipment itself. Rapid fault iso-
lation requires decisive action in selecting and imple-
menting the most appropriate fault-isolation tools. A
fault-isolation tool has the following three character-
1. It requires the least amount of time, equip-
ment, or service.
2. It is easily implemented.